Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 209.800003051758 | Thousand metric tons | NA |
| 2004 | 193.199996948242 | Thousand metric tons | -7.91% |
| 2005 | 245.100006103516 | Thousand metric tons | 26.86% |
| 2006 | 257.200012207031 | Thousand metric tons | 4.94% |
| 2007 | 260 | Thousand metric tons | 1.09% |
